The disclosure is related to vehicle identification in general and particularly to systems and methods for automatic identification and recording of vehicles passing a road user charging point or location. More particularly the disclosure is related to an on-board-unit (OBU) that can be mounted in a vehicle and provides a novel solution to the powering of such on-board-units.
Systems for road user charging have been in operation on many locations around the world. Due to increasing congestion of roads and highways and the associated environmental influences, there is an increased focus all over the world on trying to implement regulations that may reduce the amount of vehicle traffic. Levying road user charges is an option, and automated systems for easy and effective payment of road user charges are commercially available today and are also under continuous development.
One way of identifying a car that is passing a road charging point is by equipping the cars with on-board-units (OBUs), each OBU being uniquely associated with a car in which the OBU is mounted and capable of signaling its presence to an appropriate reader unit (RU) which is coupled to associated roadside equipment (RSE) for further preparation and processing of the communication signals.
In a system provided by the Norwegian company Q-Free ASA any car carrying a Q-Free badge will be automatically identified when passing a road charging point equipped with corresponding Q-Free reader unit (RU) and roadside equipment. The Q-Free system ensures correct payment, for example by debiting a prepaid customer account, each time a vehicle passes a road charging point. The badge/OBU includes a transponder that is capable of receiving a transmitted signal from the reader unit coupled to the roadside equipment and for providing a response signal from the transponder to the RU. The response uniquely identifies the vehicle. Early generations of the Q-Free system used passive transponders that could operate without electric batteries locally in the OBUs.
Present systems for road user charging (RUC) may use transponders based on Dedicated Short Range Communication (DSRC) operating at signal frequencies in the 5.8 MHz band. They may be adapted to satisfy the recommendations of the CEN/TC 278 standardization work. Such transponders are mounted in the vehicles and they are generally referred to as on-board-units or OBUs in this description.
Active on-board-units are typically powered by an electrical battery, for example in the form of a lithium primary cell (3.6 V, 350-900 mAh). In normal operation such a battery provides for a minimum lifetime of five years for the badge. The lifetime may however be limited strongly by the number of passages under a reading unit, as well as by the number of undesirable wake-up processes due to radio signals in the surroundings, for example radar antennae, WLAN-equipment etc.
Present active OBU's are faced with numerous limitations. For example, even though the energy supply units may operate for quite some time, they typically have to be replaced after some time.
Their lifetime is also limited due to a limited energy supply, necessitating frequent changes of batteries or even replacement of the OBUs themselves. Moreover, the lifetime depends also on external influences, such as how often the OBU's become activated by signals other than the radio beacon at a road user charging point (undesirable wake-up processes).
Thus there is a continuous effort to provide OBUs that operate in more power efficient manners, and to provide batteries with improved energy storage capacity while not increasing the weight and size of the OBUs.
On this background, there is a recognized need for OBUs with increased lifetime, to avoid unnecessary replacement of the batteries of the OBU's or the complete OBU itself.